Our invention relates to the packaging of implantable life assisting devices in general, and to the packaging of a fully implantable cardiac defibrillator in particular. Since the early work of Mieczyslaw Mirowski, substantial effort has been devoted to the development of fully automatic, implantable cardiac defibrillators. Most recently, these devices have been combined with bradycardia pacing and cardioversion pacing in addition to their defibrillating functionality. From the beginning, it has been recognized that such an implantable defibrillator should have a small size as an essential characteristic, particularly because it must be implanted within the patient's body. Efforts have also been made to isolate the defibrillator components from corrosive attack by biological fluids within the body and to isolate certain defibrillator components from the effects of other components, such as energy storage devices, should these components release gases or fluids. In particular, batteries and the requisite high voltage capacitors have presented challenges to the designers of defibrillator packages.
In general, the prior art has incorporated large cylindrical power capacitors into the packaging of the implantable defibrillator. A representative design is disclosed in U.S. Pat. No. 4,254,775. The packaging described in the '775 patent shows a implantable defibrillator having mutually orthogonal dimensions of height, width and thickness. The first two dimensions, height and width, are substantially larger than the remaining dimension, thickness. Tubular or cylindrical power capacitors are shown which extend substantially the entire thickness of the packaging. The diametrical dimension of power capacitors, therefore, have been a substantial limitation on the design of packaging for implantable defibrillators.
More recently, flat power capacitors have been proposed for use in defibrillators. For example, U.S. Pat. No. 5,131,388 proposes the manufacture of a flat electrolytic capacitor. The design shows a packaging having, once again, three orthogonal dimensions of height, width and thickness, with height and width being substantially larger than the thickness. As shown in the design in the '388 patent, the power capacitors and the electronic of the defibrillator lie in substantially the same plane defined by the height and width dimensions and have substantially the same thickness. In fact, the power capacitor partially surrounds the electronics on three sides.
Although progress has been made in packaging implantable defibrillators, there remains a need for improved packaging, particularly packaging which can rapidly accommodate changes in electronics, battery and power capacitor technologies. We believe that the design should accommodate changes in any one of these three principle components of a implantable defibrillator system without requiring corresponding alterations in another system. Our invention is directed towards these needs.